Absorption and mobility of radio-labelled calcium in chili pepper plants and sweet cherry trees

Calcium (Ca) is often supplied to crop species to prevent the occurrence of Ca-related disorders. Mechanisms of Ca absorption and transport are not fully understood and the effectiveness of root and/or foliar Ca fertilization may be variable. To characterize the rate of Ca absorption and transport, trials were developed with chili pepper and sweet cherry plants, using (CaCl2)-Ca-45 as a tracer. The Ca treatments supplied were: (1) No Ca-45 (control); (2) Ca-45 soil application; (3) Ca-45 supply to basal leaves, and (4) Ca-45 application to apical leaves. After two months, plants were harvested for biomass and Ca content determination. The recovery of Ca-45 in different plant parts was measured with a liquid scintillation counter and leaf traits were observed by scanning electronic microscopy. In general, the highest Ca-45 concentrations were recovered in treated organs, while root applications led to highest Ca-45 translocation rates, which varied between chili pepper and cherry plants. For chili pepper, Ca-45 applied to the soil was detected mainly in roots (44 %) followed by leaves (36.6 %) stems (17.4 %) and fruits (2 %). In sweet cherry trees, soil-applied Ca-45 was principally recovered in roots (45.3 %), shoots (28.5 %), leaves (14.3 %) and trunks (11.9 %). The results provide evidence of increased absorption of root-applied Ca, as well as different degrees of Ca mobility between species. Foliar application led to major Ca increases in treated leaves, with Ca transported to other plant organs after apical leaf Ca supply chiefly in cherry trees.